Looks like an exhaust system- the hose sits on the engine exhaust pipe and the blower on the ceiling vents the fumes out to the roof.
So you don't get carbon monoxide poisoning from running the vehicle in an enclosed bay. They hook that up to the exhaust of the vehicle and blow it outside.
What are the other two that are down hooked up to?
Nothing
Looks like extraction. Motor at the top, and duct through the roof…
To suck engine exhaust to the outside? Start the fan first, then hook the tube to the engine exhaust.
Looks like an air exhaust. You can see the blower on the left. And then it connects to the top of the roof. To exhaust. It might run in reverse pulling fresh air in. Not sure. But as you can see in the photo other examples of this tube being pulled down to the work area. So if you're working on an engine you don't want to asphyxiate your workers you would need to exhaust the exhaust
This would make sense, although I seem to remember being told that hosing can be used to pump warm air from the top of the warehouse down. So cheap , environmentally friendly heating.
If OP knows weather it sucks or blows, we might have this one solved!
You can see that the hose enters the center of a centrifugal blower, which is the inlet, so the hoses are sucking.
